Data files must be secured, especially if they were stored on a portable media device (USB thumb drive, CD, DVD) or a notebook computer. In addition to securing the data, the files must also be duplicated in a safe place.
I backup all of my data files that are stored on my notebook to the network server and to my external hard disk 20 or 30 times a day, using FileBack PC.
All data files are stored in a TrueCrypt encrypted file which is on my D: drive. They are absolutely secure from unauthorized access so long as I put my notebook into standby, hibernate, or power off mode, when I walk away from the computer. These data files are duplicated on my network server and an external hard disk during each data backup process. The data files are also duplicated on another computer, but this is only because I am so rigorous in my procedures, that I want three available backup copies of my data files.
By keeping my Microsoft Windows XP swap file and all data files on the D:, my C: does not fragment very much. However, I still defragment all of my drives at least twice a week using Diskeeper. This application was written by the folk who created Microsoft Windows defragmenter utility, and it is a much more efficient defragmenting application.